1. Field of the Invention
The invention relates to a dipole loop (folded dipole) or monopole loop.
2. Description of the Related Art
A dipole loop or folded dipole consists of two closely adjacent lambda/2 dipoles, connected at the ends, but only one of which is fed. The same current direction is set on the dipoles. Both dipoles support one another in their action. By means of different thicknesses of the two dipoles the input impedance can be influenced via transformatory effects. A so-called monopole loop, which can be interpreted as a half dipole loop on a conducting plane and consists of two lamda/4 long dipoles, which again are arranged closely adjacent and are connected to one another at the upper end, acts on the same principle. Dipole or monopole loops of this kind on a conducting plane are used as transmitting and receiving aerials in the short- and ultra-short-wave range in various embodiments.
Radio operation is also carried out in the so-called threshold wave range in amateur and also military radio. The lowest practical frequency is approximately 1.5 MHz, which corresponds to a wavelength of just under 200 meters. A conventional lambda/2 aerial would consequently have a length of approximately 100 meters, the implementation of which as a horizontal or vertical aerial means a considerable mechanical outlay. It is known to shorten such aerials mechanically with respect to their theoretical length and to balance the associated disadvantage in efficiency by suitable measures, such as roof capacities and/or series inductivities, but these known solutions also require a further considerable outlay, especially with, an aerial in multi-band operation.